There have been various different types and kinds of full color video display systems. Inventive techniques for producing such a full-color display include the use of direct view video or television monitors.
While such techniques have been satisfactory for some applications, direct video and television monitors are generally limited with respect to the size of the viewing image, due to the limited screen area associated with the cathode ray tube employed by such monitor units. Moreover, such systems have been relatively expensive to manufacture, since direct view video monitors are expensive.
Therefore, it would be highly desirable to have a new and improved full-color display system, which can produce a large television image for group viewing, without employing an expensive large direct view television monitor.
One attempt to over come the problem of having a limited viewing area has been to employ a rear view projection system, where a set of red, green and blue images are projected onto the rear side of a large transparent screen for viewing purposes. While this technique may satisfactory for some applications, it has proven to be relatively expensive to manufacture and requires a large cumbersome display unit cabinet which is difficult to move from place to place. In addition, the brightness of the viewed images is somewhat restricted or impaired due to the loss of light in traversing the transparent screen.
Therefore, it would be highly desirable to have a new and improved video display system for displaying large color images produced from a television signal which would be relatively inexpensive and that would not be difficult to move from place to place for viewing purposes.
Another attempt to overcome the problem associated with poor luminance in a large screen viewing system, has been to employ a direct front projection system. The direct projection system is similar to the rear view system except that the red, green and blue images are projected onto the front surface of a large reflective screen from a projection unit disposed in front of the screen. Again, while such a technique has proven satisfactory for some applications, the projection unit has typically been mounted in a permanent location relative to the screen, for proper focusing and to assure that a sufficient amount of light is projected onto the screen to provide an image with sufficient brightness for viewing purposes.
Therefore, it would be highly desirable to produce large screen viewing images having a relatively high luminance level and not being required to be permanently mounted or otherwise positioned.
Another attempt to overcome the problem associated with poor luminance has been to use a high speed active matrix panel with an overhead projector for the display of information. Such flat high speed active matrix panels have been capable of producing full color displays with thousands of bright colors. Such a large number of colors however has been possible only by using very sophisticated duty cycling techniques so that individual pixels in the liquid crystal display device may be selectively modulated to produce multiple intensity levels. While such duty cycle techniques have been successful for the high speed active matrix liquid crystal panels, a less sophisticated approach may be warranted for slower speed active matrix panels. Therefore, it would be highly desirable to be able to produce thousands of different bright colors in a low speed liquid crystal display panel without using a sophisticated duty cycle technique.